The technological research for reducing fuel consumption and emission of pollutants of the internal combustion engines has led the manufacturers to optimize the manufacturing process of the engine components in order to achieve ever higher machining accuracy.
The demand for higher standards of quality in the machining of some components, such as the valve seats, has increased significantly over the last few years.
Different types of so-called electronic plug gauges for checking dimensions of a valve seat and its associated valve guide are known on the market. The gauges are usually operated by an operator's hand which manually positions the gauge into the valve seat and valve guide to be checked.
As a consequence, all the measures detected by the gauges are affected by the inevitable interaction between the gauge and the operator.
A solution to this problem is disclosed in the US patent application published under No. 2005/0279159 which describes a valve seat gauging system with a gauge, wherein there is no operator's manual intervention on the gauge during the measurement procedure. The system includes a gauge head movably connected to a gauge support, which in turn is connected to a support frame by means of a system of movable arms enabling the gauge support to move in all three dimensions. An adjustable balancing system (consisting in a balancing arm in the preferred embodiment of FIG. 3 or included in a main body in the alternative embodiment of FIG. 6) exerts a pre-determined load onto the gauge support.
In the embodiment of FIG. 3, thanks to the presence of the system of movable arms, during the measurement cycle (that is after the operator has moved the gauge into position over the valve seat to be checked and release it) the gauge support is decoupled from any forces except for the predetermined load exerted by the balancing system.
According to the alternative embodiment of FIG. 6, the gauging system includes, in addition to the first gauge head, a second gauge head, or a component having the same form as a gauge head, which is inserted in the valve seat adjacent to the valve seat to be checked in order to locate the first gauge head.
Also in this case, the first gauge head is decoupled from any forces except for the predetermined load exerted by the balancing system.
However, in the systems described in the publication No. 2005/0279159 the complex mechanical connection between the gauge head and the support frame can cause, during the measurement cycle, unwanted forces deriving from the interaction of the components of the gauging system. Also the structure of the system of movable arms itself is not simple and can experience frictions or other forces between its different parts.
Moreover the predetermined load exerted by the balancing system needs an accurate regulation, which otherwise inevitably affects the measurement.